1. Field of the Invention
The present invention relates to a RECORDING APPARATUS FOR ELECTROCARDIOGRAPHS.
2. Description of the Related Background Art
The Holter electrocardiogram method is one technique to collect and analyze electrocardiogram waveforms. According to the Holter electrocardiogram method, electrocardiogram waveforms obtained for a subject and are recorded for a relatively long time, e.g., 24 hours or longer, and then are automatically analyzed by an analyzing system. Since the recording is executed for a long time, a small size and a light weight are also required for a recording apparatus of the electrocardiogram waveforms so that it can be carried out by the subject for a long time. An analog tape recorder is generally used as a conventional recording apparatus of electrocardiograms. Electrocardiogram waveforms are recorded to a compact cassette, a microcassette, or the like at a low speed by the analog tape recorder.
Detection and discrimination of an arrhythmia can be one of the analysis items of the electrocardiogram waveforms. In the diagnosis of an arrhythmia, a morphology abnormality of the electrocardiogram waveform is observed together with a rhythm abnormality of the heartbeat.
However, most of the portion of the electrocardiogram width, the portion of S-T, and the like of the electrocardiogram signal are constructed by signal components of a direct current. Therefore, when the electrocardiogram signal is directly magnetically recorded by running a magnetic tape at an extremely low speed as in the conventional electrocardiogram recording apparatus, the occurrence of a waveform distortion cannot be avoided and it is difficult to accurately record the electrocardiogram signal. Also, because it is necessary to record the electrocardiogram signal for a long time, e.g., about 24 hours, there is a problem in that the size of the battery providing the power inevitably increases and portability of the apparatus deteriorates.
A method whereby an electrocardiogram signal is converted into a digital signal and recorded is considered as one of the methods of accurately recording an electrocardiogram signal (refer to JP-A-1-104247). However, even if the above method is used, electric power consumption cannot be reduced and there is a problem in that the above method is still insufficient as a countermeasure. In JP-A-1-48236, there has been disclosed a method whereby an electrocardiogram waveform is selected, the selected electrocardiogram waveform is converted into the digital signal, electrocardiogram waveforms obtained in a predetermined period of time and displayed by a display section are observed, and when the waveform to be recorded appears, an instruction to start the recording is generated from an operating section, thereby recording the electrocardiogram waveform.
However, in the above conventional technique, many electrocardiogram waveforms must always be observed in order to selectively record only a desired electrocardiogram waveform. With respect to such point, there is a problem in that it is difficult to apply the above technique to the Holter electrocardiogram method. On the other hand, the foregoing morphology abnormality of the electrocardiogram waveform is discriminated by comparing with the normal electrocardiogram waveform and is classified into the morphology. The electrocardiogram waveforms regarding the respective classified morphologies and the appearance frequencies of the electrocardiogram waveforms of the respective morphologies are used together with the foregoing rhythm abnormality of the heartbeat as references for a medical diagnosis. However, there is a problem in that there is no established reference as a method of classifying the morphology of the electrocardiogram waveform.
In JP-A-57-96638, there has been proposed a technique to quantitatively analyze an electrocardiogram waveform by applying an analyzing method called a Lorentz plot to a generation period of electrocardiogram waveforms. However, in the above conventional technique, various analyses are mainly executed by paying attention to the generation period of the electrocardiogram waveforms and there is a problem in that nothing is disclosed with respect to the morphology classification of the electrocardiogram waveform.